Oxidized, degraded interpolymer of ethylene and propylene and fuel composition containing the same



United States Patent Office 3,374,073 Patented Mar. 19, 1968 OXIDIZED, DEGRADED INTERPOLYMER OF ETHYLENE AND PROPYLENE AND FUEL COMPOSITION CONTAINING THE SAME William C. Gorge], Mayfield Heights, Ohio, assignor to The Lubrizol Corporation, Wickliffe, Ohio, a corporation of Ohio No Drawing. Filed-lune 23, 1964, Ser. No. 377,382 8 Claims. (Cl. 44-62) The present invention relates to improved hydrocarbon fuel oil compositions. It relates more particularly to such compositions which have improved flow and pour properties by virtue of the incorporation therein of a minor proportion of an oxidized, degraded interpolymer of propylene and ethylene.

The pour point of an oil, generally speaking, is the lowest temperature at which the oil will pour or flow when chilled without disturbance. The problems associated with pour point ordinarily have to do with the storage and use of heavy oils such as lubricating oils, but the recent increased use of distillate fuel oils have revealed similar problems even with these lighter, more fluid materials. Pour point problems arise through the formation of solid or semi-solid waxy particles in an oil composition. In the storage of furnace oils or diesel oils during the winter months, for example, temperatures may decrease to as low as 15 F. to -50 F. The decreased temperatnres often cause crystallization and solidification of wax in the distillate fuel oil so that pumping or syphoning is rendered difllcult or impossible. Furthermore, at such temperatures the flow of the oil through the filters cannot be maintained, and the result is a failure of the equipment.

This difiiculty has been remedied in some instances by using lighter fractions as fuel oils, i.e., by lowering the maximum distillation temperature at which a distillate fraction is collected. It has also been suggested that the distillate fuel oils be dewaxed such as by urea dewaxing. Separately or in combination, these remedies are, however, economically prohibitive. That is, readjustment of end points causes the loss of valuable blending material for distillate fuel stocks and dewaxing operations are eX- pensive.

Another approach to the problem has involved a search for a pour point depressant which will decrease the pour point of the distillate fuel oil. Unfortunately, pour point depressants which are normally effective in lubricating oils and other heavy oils are generally ineffective in a distillate fuel oil.

The principal object of this invention is, therefore, to provide fuel oil compositions having improved pour properties at low temperatures.

Another object of this invention is to provide a process for the oxidative degradation of interpolymers of ethylene and propylene.

Still another object of this invention is to provide novel compositions of matter.

These and other objects are accomplished by providing an improved hydrocarbon fuel composition comprising a major proportion of a hydrocarbon fuel oil and from about 0.001 t about 3% by weight of an oxidized, degraded interpolymer of propylene and ethylene prepared by contacting an interpolymer of propylene and ethylene having a molecular weight of from about 50,000 to about 800,000 with an oxygen containing gas at a temperature of at least 100 C. for a time sufiicient to reduce the molecular weight to a value within the range of from about 3,000 to about 5% less than the molecular weight before degradation, said interpolymer comprising from about 20 to about 66 mole percent of propylene and from about 33 to about 80 mole percent of ethylene.

The interpolymers of this invention are derived principally from ethylene and propylene. They may, however, include minor amounts, e.g., from about 1 to about 10 mole percent, of other monomers. Examples of these other monomers include materials having the general formula, RCH=CH wherein R is an alkyl radical containing from 2 to 8 carbon atoms. Examples of the latter include butene-l, hexene-l, 4-methyl-1-pentene, and decene-l. The other monomer may also be an olefinic compound having a plurality of double bonds, in particular, a diolefin containing from 5 to 25 carbon atoms, e.g., 1,3-hexadiene, 1,4-pentadiene 1,5-hexadiene, Z-methyl- 1,5-hexadiene, 3,3-dirnethyl-l,S-heXadiene, 1,7-octadiene, 1,9-decadiene, 1,19-eicosadiene, and dicyclopentadiene. Preferably, the interpolymers are copolymer of ethylene and propylene or terpolymers of ethylene, propylene, and up to 10 mole percent, but not more than 20 percent by weight, of a nonconjugated diolefin which contains from about 5 to about 25 carbon atoms. Interpolymers containing from about 20 to about 66 mole percent of propylene and from about 33 to about mole percent of ethylene are useful for the purposes of this invention. However, copolymers containing from about 25 to about 40 mole percent of propylene and from about 60 to about 75 mole percent of ethylene are especially preferred and terpolymers containing 30 to 50 mole percent of propylene, 50 to 70 mole percent of ethylene, and up to 10% by Weight of a nonconjugated diolefin are also preferred.

The third monomer of the above described terpolymers is a nonconjugated diolefin containing from about 5 to about 25 carbon atoms, or a mixture of such nonconjugated diolefins. Nonconjugated diolefins preferred for the purposes of this invention include 6-methyl-1,5-heptadiene, 1,4-hexadiene, 11-ethyl-1,1l-tridecadiene, 1,5-hexadiene, 2-alkylnorbornadienes (especially 2-methyl norbornadienes), and 5-methylene-2-norbornene. Especially preferred are the aliphatic acyclic diolefins containing from 5 to 25 carbon atoms in which the double bonds are separated by more than 2 carbon atoms and in which at least one double bond is located in the terminal position.

The molecular weight indicated above is calculated from the reduced specific viscosity of the interpolymer. This calculation is made using the following equation:

RS V=AM wherein RSV is the reduced specific viscosity, and M is the molecular weight; A is 0.000100 and x is 0.80 for polypropylene (Kirk-Othrner, Encyclopedia of Chemical Technology, 663 (2nd Supp. 1960)); and A is 0.000677 and x is 0.67 for polyethylene (Gaylord and Mark, Linear and Stereoregular Addition Polymers, 79 (1959)). The values of A and x are obtained by linear interpolation between the above values for interpolymers of ethylene and propylene, based on the relative molar proportions of the monomers, e.g., for a copolymer containing 30 mole percent of propylene and 70 mole percent of ethylene, A is 0.000504 and x is 0.709. The same sort of calculation may be used for estimating the molecular weight of the terpolymers of this invention by assuming the effect of the third monomer, usually present at less than 10 percent by weight, to be negligible.

The term reduced specific viscosity means the specific viscosity, corrected to zero shear gradient, divided by the concentration of the solution in grams per milliliters. The viscosity is measured at C. on a solution of interpolymer in decalin containing 0.1 gram of the interpolymer in 100 milliliters of the solution.

Interpolymers having molecular weights of from about 50,000 to about 800,000 are useful for the purposes of this invention. The indicated molecular Weight range of from about 50,000 to about 800,000 corresponds to a range of reduced specific viscosity of from about 1 to about 5. The preferred molecular weight range is from about 80,000 to about 600,000 and this corresponds to a reduced specific viscosity range of from about 1.3 to about 4.

The term substantially amorphous indicates that a certain degree of crystallinity in the interpolymer is permissible. Highly crystalline interpolymers are relatively insoluble in fuel oil, especially at lower temperatures. A simple procedure for determining the degree of crystallinity of the interpolymers consists of mixing a known quantity, e.g., 5 grams of a given interpolymer with n-heptane (100 milliliters), the quantity of the insoluble proportion being taken as a measure of the degree of crystallinity. Interpolymers useful for the purposes of this invention should show no more than about 5% by weight of such insoluble proportion (in n-heptane) at C., and preferably, this insoluble proportion should be no more than about 3 by weight.

Amorphous interpolymers of the type described can be prepared by any of several methods known in the art. They can be prepared, for example, by copolymerizing ethylene and propylene under relatively mild conditions of temperature and pressure in the presence of a Ziegler type catalyst, viz., a mixture of a compound derived from a Group IV, V or VI metal of the Periodic Table in combination with an organo metallic compound of a Group I, II, or III metal of the Periodic Table.

The Group IV-VI metals that are useful as indicated include titanium, zirconium, halfnium, thorium, uranium, vanadium, niobium, tantalum, chromium, molybdenum, selenium, tellurium, and tungsten. Halides, oxychlorides, acetylacetonates, alcoholates, oxides, complex halides such as the fluorotitanates and fluorozirconates, acetates, and benzoates, of the indicated metals are useful components of the above-indicated catalyst system. The salts of titanium, zirconium, chromium, thorium, vanadium, and uranium are particularly effective. Examples of such compounds include titanium tetrachloride, titanium trichloride, titanium dichloride, tetrabutyl titanate, vanadium tetrachloride, vanadyl trichloride, vanadium trichloride, vanadium triacetylacetonate, vanadium oxyacetylacetonate, zirconium tetrachloride, zirconium acetylacetonate, chromium acetylacetonate, etc.

Group I-III metals from which the organo metallic compound is derived include the alkali metals, the alkaline earth metals, zinc, earth metals, and the rare earth metals. Examples of the organometallic compound include alkali metal alkyls or aryls such as butyllithium, amylsodium, phenylsodium, etc., dimethylmagnesium, diethylmagnesium, diethylzinc, butylmagnesium chloride, phenylmagnesium bromide, alkylor aryl-aluminum compounds as, for example, triethylaluminum, tripropylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, dimethylaluminum chloride, diethylaluminum chloride, ethylaluminum dichloride, the equimolar mixture of the latter two, known as aluminum sesquichloride, diisobutylaluminum chloride or fluoride, etc., and complexes of such organo metallic compounds as, for example, sodium aluminum tetraethyl, lithium aluminum tetraoctyl, etc.

Efi'ective catalyst combinations of the type described include in combination: aluminum triisobutyl and vanadyl trichloride; aluminum triisobutyl, aluminum chloride, and vanadyl trichloride; vanadium tetrachloride and aluminum trihexyl; vanadyl trichloride and aluminum trihexyl; vanadium triacetylacetonate and aluminum diethyl chloride; titanium tetrachloride and aluminum trihexyl; vanadium trichloride and aluminum trihexyl; titanium trichloride and aluminum trihexyl; titanium dichloride and aluminum trihexyl; etc. Most preferred are combinations of titanium and vanadium halides, oxyhalides or alcohol-ates with lithium, sodium, magnesium and aluminum alkyls.

The polymerization usually is carried out by mixing the two catalyst components in a diluent such as a hydrocarbon solvent and then passing ethylene and propylene into the catalyst mixture at atmospheric or slightly elevated pressure and at room temperature or moderately elevated temperature.

Alternatively, the interpolymers can be prepared by the method described in Belgian Patent 535,082 wherein a monomer mixture including ethylene and propylene is contacted with a catalyst containing as the essential ingredients an oxide of chromium associated with an oxide of silicon, aluminum, zirconium, or thorium. Such interpolymers may also be prepared by the methods described in U.S. 2,700,633, 2,792,288, and 2,726,231 in which the copolymerization of ethylene and propylene is accomplished by bringing a mixture of the two monomers into contact with a subhexavalent molybdenum-oxygen compound combined with an active alumina, titania, or zirconia support at a temperature between-about 100 C. and 300 C., and a pressure between atmospheric and 5000 p.s.i.g.

Because the monomers do not polymerize at the same rate, i.e., ethylene polymerizes faster than propylene, the ratio of the starting mixture of monomer is not the same as that desired in the final product and this is, of course, a major consideration in the preparation of a particular final product. For example, the polymerization may be carried out in n-heptane at 2565 C. under normal pressure and in the presence of a catalyst prepared by adding vanadyl trichloride to aluminum trihexyl in a molar ratio of 1:3. Under these conditions, the starting mixture of monomers should comprise from about 25 to about 50 mole percent of ethylene and from about 50 to about 75 mole percent of propylene to obtain the interpolymers as described above, i.e., having a propylene content of from about 20 to about 45 mole percent and an ethylene content of from about 55 to about mole percent. The interpolymers of propylene, ethylene, and a non-conjugated diolefin may be prepared using the catalyst systems and molar proportions of ethylene and propylene as indicated above. However, inclusion of a non-conjugated diene does have an effect on the relative amounts of the ethylene and propylene incorporated, i.e., incorporation of a small amount of a nonconjugated diene in the polymerization causes a decrease in the amount of propylene incorporated from any particular ethylene-propylene gas mixture. Descriptions of how these terpolymers may be prepared are found in the following patents: U.S. 2,933,- 480, U.S. 3,000,866, U.S. 3,063,973, and U.S. 3,093,621.

When the polymerization is carried out in a solvent, the production of amorphous interpolymer is favored. Often, an extraction with n-heptane will assure the amorphous quality of the interpolymer so that it meets the solubility requirements as aforesaid. Such an extraction is especially desirable where the interpolymer is not prepared in a solvent.

The following examples are illustrative of the preparation of interpolymers useful for the purposes of this invention. All parts and percentages are by weight unless otherwise indicated.

Example 1 Tetrachloroethylene (3 liters) is passed through a silica gel column, sparged with nitrogen and then added under nitrogen to a dry reaction flask at 25 C. Agitation is begun and an equimolar mixture of gaseous ethylene and propylene is introduced below the tetrachloroethylene liquid surface at a rate of milliliters per second until a saturated monomer solution is obtained, the excess of gas being allowed to escape through a gas outlet tube. To this saturated monomer solution there is added 8 milliliters (0.0128 mole) of a 1.6 molar solution of aluminum triisobutyl in cyclohexane and 0.94 milliliter (0.010 mole) of vanadyl trichloride, separately and rapidly in turn, by means of syringes, through an opening in the reactor sealed with a soft rubber cap. The tetrachloroethylene solution turns a clear amber color and the temperature rises to about 40 C. after a minute. To the agitated reaction mixture at 35 40 C., an equimolar mixture of gaseous ethylene and propylene is introduced at a rate of 100 milliliters per second over a period of 0.5 hour. To the reaction mixture there is added 5 milliliters of n-butanol and the polymer separates as a rubbery swollen solid which is squeezed free of excess solvent, washed several times with fresh n-butanol, and dried. The copolymer thereby obtained has a propylene content of 20 mole percent.

Example 2 A solution of 30 grams (0.15 mole) of aluminum triisobutyl and 84 grams (0.6 mole) of decene-l in 200 milliliters of tetrachloroethylene was heated to boiling under reflux and under a nitrogen atmosphere for 2 hours to form aluminum tridecyl. The solution was cooled to room temperature and blended with 1800 milliliters of tetrachloroethylene, pre-saturated with an ethylene, propylene gas mixture containing 75 mole percent of propylene. The ethylene, propylene gas mixture (75 mole percent propylene) is fed into the tetrachloroethylene solution at a rate of 37.5 milliliters per second. Introduction of ethylene and propylene is continued as a solution of 4.35 grams (0.025 mole) of va-nadyl trichloride in 100 milliliters of tetrachloroethylene is added to the reaction mixture with vigorous stirring at 294l C. over a period of 2 minutes. The catalyst forms a clear violet solution and rapid absorption of the gas feed commences. Thereafter, 30 milliliters (0.108 mole) of a 3.6 molar solution of 1,4-hexadiene in tetrachloroethylene is added over a period of 9 minutes to the reaction mixture at 4148 C. The feed of ethylene and propylene is continued and 53.4 milliliters (0.192 mole) more of the 3.6 molar 1,4-hexadiene solution is added to the reaction mixture over a period of 2 hours at 3840 C. Then, 6 liters of n-butanol are added to the reaction mixture causing precipitation of an interpolymer. The precipitate is slurried with acetone in a Waring Blendor and then dried on a rubber mill at 50 C. The product (97 grams) is a soft, rubbery terpolymer which has a propylene content of 42 mole percent, a diene content of 1.2 mole percent corresponding to an iodine number of 8.9, and, by difference, an ethylene content of 56.8 mole'percent. The terpolymer has an RSV of about 2.1, corresponding to a molecular weight of 125,500.

The oxidized, degraded interpolymers of the hydrocarbon fuel compositions of this invention are prepared by subjecting the interpolymers described as useful for the purposes of this invention to oxidative degradation. This degradation is carried out at a temperature of at least 100 C., up to the decomposition temperature of the in terpolymer, in the presence of oxygen for a time sufiicient to reduce the molecular weight of the interpolymer to a maximum molecular weight after degradation of about 5% less than the molecular weight of the interpolymer before degradation and a minimum molecular weight after degradation of about 3,000. Thus, for example, utilization of an oxidized, degraded interpolymer having a molecular weight of from about 3,000 to about 190,000 derived by oxidizing and degrading an interpolymer of this invention having a molecular weight of 200,000, is contemplated.

In terms of RSV, the molecular weight of the oxidized, degraded interpolymer may range from about 0.15 to about 4.95, corresponding to a molecular weight range of 3,000 to 760,000. Preferably, the oxidized, degraded interpolymer has an RSV of from about 0.2 to about 1, corresponding to a molecular weight range of from about 5,000 to about 90,000, but at least 5% less than the molecular weight before degradation.

In the indicated oxidative degradation, the character of the interpolymer is varied in two distinct ways, viz., the molecular weight of the interpolymer is decreased as measured by RSV and oxygen is incorporated into the interpolymer. The oxygen reacts with the interpolymer to form carboxylic acids, ketones, and aldehydes, evidenced by the detection of carboxy and carbonyl radicals in the oxidized, degraded interpolymer.

The oxygen required during the oxidative degradation may be in the form of oxygen, oxygen in admixture with a gas inert under the circumstances, e.g., the oxygen in air, or an oxygen producing compound, i.e., a compound, preferably gaseous, which liberates oxygen alone or in admixture with a gas inert under the circumstances at above C. The term oxygen containing gas, as used in this specification, includes oxygen and the indicated mixtures, preformed or evolved in situ.

The oxidized, degraded interpolymer may be prepared by mechanical shearing wherein large areas of surface are formed, heated and exposed to air, by contacting hot oxygen or air, i.e., above 100 C., with the surface of the interpolymer, or by bubbling an oxygen containing gas through a solution of the interpolymer in an organic solvent. Of these methods, oxidative degradation of an interpolymer dissolved in an organic solvent appears to be most efiicient.

Solvents useful for preparing solutions of the interpolymers of this invention for degradation include kerosene, xylene, decahydronaphthalene, cyclohexane, cumene, diphenyloxide, and mixtures of diphenyl oxide (at least about 70% by weight) and biphenyl. However, solvents selected from the class consisting of diphenyl oxide and mixtures of diphenyl oxide with biphenyl are especially desirable because they can dissolve as much as 40% by weight of the interpolymers, while with the other solvents the concentration is often limited to 3-8% by weight and the upper temperature limit is usually about 200 C.

Preferably, the oxidized, degraded interpolymers of this invention are prepared by a process comprising bubbling an oxygen containing gas through a solution of from 5 to about 40% by weight of an interpolymer of ethylene and propylene having a molecular weight of from about 50,000 to about 800,000 in a solvent, at a temperature of from about 100 C. up to about the boiling point of the solvent for a time sufiicient to reduce the molecular Weight of the interpolymer to a value within the range of from about 3,000 to about 5% less than the molecular Weight before degradation, said interpolymer of propylene and ethylene comprising from about 20 to about 66 mole percent of propylene and from about 33 to about 80 mole percent of ethylene, said solvent being selected from the class consisting of diphenyl oxide and mixtures of diphenyl oxide with biphenyl.

The preferred procedure, involving the use of a solvent selected from the class consisting of diphenyl oxide and mixture of diphenyl oxide with biphenyl, is most efi'iciently carried out at a temperature from about C. to about 240 C. At these temperatures, the solution is fluid enough to allow reaction at a reasonable rate, while the problem of solvent loss by entrainment in the oxygen containing gas stream is not serious. The process may also be facilitated by gradually adding the interpolymer to the solvent and beginning the oxidative degradation at once. When air is used, flow rates of from about one to about 10 cu. ft./hr./lb. of solution for 0.5-30 hours may be used to accomplish the desired degree of degradation.

The following examples are illustrative of the oxidative degradation process of this invention:

Example 3 A blend is prepared of 1200 grams of diphenyl oxide and 300 grams of an ethylene-propylene copolymer having a propylene content of 33 mole percent and an RSV of 2.13, corresponding to a molecular Weight of 127,600. The blend is heated to 230 C. in one hour and, thereafter, air is bubbled through the reaction mixture at a rate of 0.5 cu. ft./hr, (standard) for 4.5 hours. The blend is allowed to cool, and then is heated to 230 C. whereupon air is bubbled through the blend at 230 C. for an hour at a rate of 0.5 cu. ft./hr. (standard), after which the blend is permitted to cool again. The procedure, viz.,

heating, air-blowing, and cooling, is repeated three (3) times (once with a 2-hour period of air-blowing). The oxygenated blend is heated to 210 C./0.6 mm. to remove diphenyl oxide; the residue comprises 300 grams of degraded copolymer. A portion of the degraded interpolymer (230 grams) is diluted with xylene (230 grams), heated to 130 C., and then filtered. The degraded interpolymer has an RSV of 0.384 and the 50% xylene solution thereof has a Sap. No. of 4.6 using phenolphthalein as an indicator.

Example 4 A blend is prepared from 10 pounds of a terpolymer and 40 pounds of a solvent at 225 C. The solvent is composed of 73.5% of diphenyl oxide and 26.5% of biphenyl. The terpolymer has an RSV of 2.77, corresponding to a molecular weight of 294,500, a propylene content of 38.2 mole percent, and contains about 3.5% by weight of 1,4- hexadiene, the balance of the interpolymer being ethylene. Air is bubbled through the blend at 220-230 C. at a rate of 20 cu. ft./hr. (standard) for 5 hours. A portion of the reaction mixture is heated to 260 C./ 0.5 mm. to remove solvent. The degraded terpolymer isolated thereby has an RSV of 0.495, corresponding to a molecular weight kerosene, xylene, and mixtures of kerosene and xylene are used for this purpose. Although many solvents would be operable for this purpose, practical considerations involved in handling, such as flash point, must be considered. Since the concentrates may be subjected to cold temperatures, flow at these low temperatures is also a necessary consideration. Flow characteristics also are dependent upon the oxidized, degraded interpolymer and its concentration. A solution of an oxidized, degraded interpolymer at a concentration of less than about by weight in xylene, kerosene or mixtures of xylene and kerosene meets all of the practical requirements. These solutions are prepared by stirring mixtures of the interpolymer and solvent, preferably at elevated temperatures for faster dissolution. Temperatures within the range of from about 90 C. to about 135 C. and up, but less than the solvent reflux temperature are suitable.

The data in Table I illustrate the pour point properties of the oxidized, degraded interpolymers utilized in the hydrocarbon fuel compositions of this invention. The fuel oil used in obtaining these results has a pour point of 10 F. and contains 70% by weight of a No. 2 distillate and by weight of kerosene. All pour points quoted hereafter were obtained by the method described of 26,850, and a 50% xylene solution thereof has a Sap. 25 in ASTM D-9757.

TABLE I Ethylenc-Propylene Inter-polymer Pour Point F.) of Fuel Oil Having an Interpolymer Content of Undegraded Degraded Propylene Content RSV Molecular RSV Molecular 0.01% 0.02% 0.025% 0.03% 0.04% 0.05% (Mole Percent) Weight Weight 1 32. 5 2. 10 126, 400 Undegraded 10 10 1 32. 5 2. 10 126, 400 0, 10 -10 1 34. 0 1. 89 108, 200 Undegraded 10 -10 1 34. 0 1. 89 108,200 0. 396 12,150 10 1 34.0 1. 89 108, 200 0. 477 15, 790 10 20 l 33. 0 2. 13 127, 600 Undegraded -10 15 1 33.0 2. 13 127, 600 0. 384 -15 25 2 38. 2 2. 77 294, 500 Undegraded 25 2 38. 2 2. 77 294, 500 495 26, 25 -35 l The balance of the interpolymer is ethylene. 2 The interpolymer also contains about 3.5% contains 70% by weight of a No. 2 distillate and 30% No. of 1.4 using phenolphthalein as an indicator.

Although the oxidized, degraded interpolymers may be used as intermediates in various chemical reactions and as oil thickeners, among others, the principal use contemplated for these materials is as pour point depressants in fuel oils.

The fuel oils suitable for the purposes of this invention include hydrocarbon oils such as distillate and residual burner oils and diesel fuels having the following characteristics: minimum flash point, 80 F.; maximum pour point, 70 F.; maximum 10% point, 650 F.; maximum 90% point, 900 F.; minimum API gravity, 24; and maximum viscosity at 100 F., 130 SUS (Saybolt Universal seconds). They may be derived from petroleum by a variety of methods including straight distillation from crude petroleum oil and thermal or catalytic cracking of petroleum oil fractions.

The fuel oil compositions of this invention may be prepared merely by dissolving the indicated oxidized, degraded interpolymers in an appropriate fuel oil at the desired level of concentration. Generally, depending upon the fuel oil used, such dissolution will require mixing and some heating. Mixing may be accomplished by any of the many commercial methods, ordinary tank stirrers being adequate. Heating is not absolutely necessary, but mild heating, e.g., at 25-95 C., will greatly accelerate dissolution. The amount of interpolymer incorporated may be from about 0.001 to about 3 percent by weight. The range of from about 0.01 to about 0.2 percent by weight is the preferred interpolymer concentration.

Alternatively, the oxidized, degraded interpolymers may be blended with suitable solvents to form concentrates that can be readily dissolved in the appropriate fuel oils at the desired concentrations. Fluid hydrocarbons such as by weight of 1,4-hexadienc and the balance of the interpolymer is ethylene. The fuel oil, in this instance,

by weight of kerosene and has a pour point of 20 F.

What is claimed is:

1. A hydrocarbon fuel compositioncomprising a major proportion of a hydrocarbon fuel oil and from about 0.001 to about 3% by weight of an oxidized, degraded interpolymer of propylene and ethylene prepared by contacting an interpolymer of propylene and ethylene having a molecular weight of from about 50,000 to about 800,000 with an oxygen containing gas at a temperature of at least C. for a time sufficient to reduce the molecular weight to a value within the range extending from about 3,000 to about 5% less than the molecular weight before degradation, said interpolymer comprising from about 20 to about 66 mole percent of propylene and from about 33 to about 80 mole percent of ethylene.

2. The hydrocarbon fuel composition of claim 1 wherein the interploymer is a copolymer of propylene and ethylene.

3. The hydrocarbon fuel composition of claim 1 wherein the interpolymer is a terpolymer of propylene, ethylene, and up to about 20% by weight of a nonconjugated diolefin which contains from about 5 to about 25 carbon atoms.

4. The hydrocarbon fuel composition of claim 1 wherein the maximum molecular weight after degradation is less than 90,000.

5. A hydrocarbon fuel composition comprising a major proportion of a hydrocarbon fuel oil and from about 0.001 to about 3% by weight of an oxidized, degraded copolymer of propylene and ethylene prepared by contacting a copolymer of propylene and ethylene having-a molecular weight of from about 80,000 to about 600,000

with an oxygen containing gas at a temperature of at least about C. for a time sufficient to reduce the molecular weight to a value within the range of from about 3,000 to about less than the molecular weight before degradation, said copolymer comprising from about to about mole percent of propylene and from about to about mole percent of ethylene.

6. A hydrocarbon fuel composition comprising a major proportion of a hydrocarbon fuel oil and from about 0.001 to about 3% by weight of an oxidized, degraded terpolymer of propylene, ethylene, and a nonconjugated diolefin prepared by contacting a terpolymer of propylene, ethylene, and a nonconjugated diolefin having a molecular weight of from about 80,000 to about 600,000, with an oxygen containing gas at a temperature of at least C. for a time sufficient to reduce the molecular weight to a value within the range of from about 3,000 to about 5% less than the molecular weight before degradation, said terpolymer comprising from about 25 to about 50 mole percent of propylene, from about 50 to about 75 mole percent of ethylene, and containing up to 20% by weight of a nonconjugated diolefin which has from about 5 to about 25 carbon atoms.

7. The hydrocarbon fuel composition of claim 6 where- 10 in the terpolymer contains up to 10% by weight of the nonconjugated diolefin, said nonconjugated diolefin, being an aliphatic, acyclic diolefin containing from about 5 to about 25 carbon atoms, and at least one of the double bonds of said diolefin being in the terminal position.

8. The hydrocarbon fuel composition of claim 7 wherein the diolefin is 1,4-hexadiene.

References Cited UNITED STATES PATENTS 2,913,439 11/1959 Bondi et al 4470 X 3,082,192 3/1963 Kirshenbaum et a1. 260-88.2 3,153,025 10/1964 Bush et a1. 260-88.2 3,252,771 5/1966 Clough et al 44-62 FOREIGN PATENTS 848,777 9/ 1960 Great Britain.

20 DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, Assistant Examiner. 

1. A HYDROCARBON FUEL COMPOSITION COMPRISING A MAJOR PROPORTION OF A HYDROCARBON FUEL OIL AND FROM ABOUT 0.001 TO ABOUT 3% BY WEIGHT OF AN OZIDIZED, DEGRADED INTERPOLYMER OF PROPYLENE AND ETHYLENE PREPARED BY CONTACTING AN INTERPOLYMER OF PROPYLENE AND ETHYLENE HAVING A MOLECULAR WEIGHT OF FROM ABOUT 50,000 TO ABOUT 800,000 WITH AN OXYGEN CONTAINING GAS AT A TEMPERATURE OF AT LEAST 100*C. FOR A TIME SUFFICIENT TO REDUCE THE MOLECULAR WEIGHT TO A VALUE WITHI THE RANGE EXTENDING FROM ABOUT 3,000 TO ABOUT 5% LESS THAN THE MOLECULAR WEIGHT BEFORE DEGRADATION, SAID INTERPOLYMER COMPRISING FROM ABOUT 20 TO ABOUT 66 MOLE PERCENT PROPYLENE AND FROM ABOUT 33 TO ABOUT 80 MOLE PERCENT OF ETHYLENE. 